1. Cut each tenderloin crosswise into 3 to 4 pieces. Remove husks from fresh ears of corn; scrub with a stiff brush to remove silks. Rinse. Peel and cut onions into wedges, leaving root end intact (helps wedges stay together). Sprinkle tenderloin pieces, corn, onions, and zucchini lightly with salt and pepper.
2. For brush-on sauce, in a small bowl combine barbecue sauce, sage, and crushed red pepper. Divide mixture in half; set aside.
3. For a charcoal grill, arrange hot coals around a drip pan. Test for medium-hot heat above the pan. Place pork on grill rack over drip pan. Cover and grill for 35 to 40 minutes or until an instant-read thermometer registers 160 degree F. Arrange corn, onions, and squash halves directly over coals around edge of grill rack for the last 20 minutes of grilling or until tender and browned, turning occasionally. Brush pork and all the vegetables with half of the brush-on sauce the last 10 minutes of grilling. (For gas grill, preheat grill. Reduce heat to medium-hot. Adjust heat for indirect cooking. Grill as above.)
4. To serve, cut corn and squash into bite-size pieces. Arrange tomato slices in a bowl and top with vegetables and pork. Heat the remaining sauce in a small saucepan on the grill, or microcook remaining sauce in a microwave-safe bowl, covered, for 20 seconds or until heated through; stir before passing with pork and vegetables. Makes 6 servings.